Now continue the extrusions around the innter edge of the car body as shown then delete the three polys shown in red. Make sure you weld any overlapping vertices.

Time to do a bit of sculpting to get it to look right. Pull and push vertices to line up the edges shown in green with the edges on the interior. It doesn't really have to be perfect so just do the best you can. Hide the interior geometry.

Select the same edges as above and extrude them inward a little to create the polys shown in red. This will give a nice lip to this area when the geometry is smoothed.

Now hide the body and show the interior. Select the green edges and extrude them ineards like you did earlier to create the polys shown in red.

Let's move to the front of the interior now. Select the edges shown in green and extrude them in the direction of the red arrows.

Continue the extrusions, this time at more an upwards angle. Adjust vertices as needed.